PROJECT SUMMARY/ABSTRACT Food intake and energy balance are controlled by a dynamic interplay of gut-brain signaling pathways; however, the molecular underpinnings in these processes and their dysregulation in obesity remain poorly understood. Recent work from the DiPatrizio lab suggests that our bodies? cannabis-like signaling molecules, the endocannabinoids (eCBs), are critical mediators of gut-brain signaling important for food intake, and are upregulated in the gut in diet-induced obesity (DIO). These seminal studies suggest that eCB signaling in the gut is an orexigenic signal that is activated under several behavioral and metabolic conditions, and may become dysregulated in obesity. The mechanism(s) of gut-brain eCB control of food intake and reorganization of these pathways in DIO is unknown. Preliminary data, however, suggests that in DIO, increased eCB signaling in the intestinal epithelium inhibits nutrient-induced release of satiation peptides, which increases meal size and delays satiation. We propose the central hypothesis that the eCB system in the gut plays a critical role in nutrient sensing and gut-brain satiation signaling, which is remodeled after chronic exposure to high-energy nutrients and contributes to overeating in DIO. We propose the following specific aims to test this hypothesis: SA1. To determine if CB1Rs in the gut control gut-brain satiation signaling. Based on preliminary data, we hypothesize that CB1Rs in the intestinal epithelium control nutrient sensing and gut-brain satiation signaling that become dysregulated in DIO. To test this hypothesis, we will examine the role for CB1Rs in controlling feeding behavior by evaluating nutrient-induced release of satiation peptides in vivo and in vitro using our first-of-kind mouse model that conditionally lacks CB1Rs in intestinal epithelium in combination with peripherally-restricted CB1R antagonists, and enteroendocrine cell lines. This aim will provide evidence of a previously unidentified control mechanism of nutrient-induced gut-brain satiation signaling. SA2. To determine the mechanism of eCB system remodeling in DIO, and impact of dietary intervention on these pathways. The molecular underpinnings of eCB system remodeling in DIO, specific dietary components that drive this process, as well as the impact of dietary intervention on these pathways and behavioral outcomes are unknown. We hypothesize that chronic exposure to WD leads to remodeling of the eCB system in the gut, which promotes overeating and DIO. To test this hypothesis, we will use our intestinal epithelial CB1R-null mice in combination with targeted lipidomics and advanced UPLC/MS/MS-based assays of eCB system function to identify specific dietary components that drive heightened eCB system activity and overeating, and the mechanism of remodeling that occurs in DIO. Furthermore, weight loss following dieting is all-too-often met with high levels of recidivism to overeating and obesity; thus, we will assess the ability for low-calorie dietary intervention to normalize gut-brain eCB signaling in DIO.